U.S. patent number 4,773,221 [Application Number 06/396,150] was granted by the patent office on 1988-09-27 for apparatus for recovering the kinetic energy of sea waves.
This patent grant is currently assigned to Interproject Service AB. Invention is credited to Sven A. Noren.
United States Patent |
4,773,221 |
Noren |
September 27, 1988 |
Apparatus for recovering the kinetic energy of sea waves
Abstract
Apparatus for recovering kinetic energy bound in the movement of
water waves. The apparatus comprises a bouyant unit (2) and an
energy-absorbing device connected to the bouyant unit. The
energy-absorbing device comprises an immersed rigid piston (6)
which is slideably arranged in a substantially vertical, elongate
accelerating tube (1) which is intended to be immersed in the water
and which is open at both ends thereof. The accelerating tube is
connected to the buoyant unit (2) so as to accompany movement of
the unit imparted thereto by the wave movement of the water. The
working stroke (1) of the piston in the accelerating tube is
limited by means of movement-limit means (8,9) incorporated in the
accelerating tube and arranged to abrogate the force acting on the
piston. In accordance with one suitable embodiment, these
movement-limiting means comprise openings (9) arranged in the
accelerating tube and co-acting with corresponding openings (8) in
the piston (6).
Inventors: |
Noren; Sven A. (Bromma,
SE) |
Assignee: |
Interproject Service AB
(Bettna, SE)
|
Family
ID: |
20344265 |
Appl.
No.: |
06/396,150 |
Filed: |
July 8, 1982 |
Foreign Application Priority Data
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Jul 16, 1981 [SE] |
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8104407 |
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Current U.S.
Class: |
60/501; 60/502;
60/497 |
Current CPC
Class: |
F03B
13/187 (20130101); Y02E 10/30 (20130101); Y02E
10/38 (20130101) |
Current International
Class: |
F03B
13/18 (20060101); F03B 13/00 (20060101); F03B
013/12 () |
Field of
Search: |
;60/495,497,501,502
;290/53,54 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ostrager; Allen M.
Attorney, Agent or Firm: Bauer & Schaffer
Claims
What is claimed:
1. In apparatus for recovering kinetic energy bound in the movement
of water waves, having a bouyant unit and an energy-absorbing
device connected to the bouyant unit comprising an immersed rigid
piston slideably arranged in a substantially vertical, elongate
accelerating tube immersed in said water, said tube being open at
both ends and connected to the bouyant unit so as to accompany the
movement of said unit imparted thereto by said wave movement, the
improvement including means for limiting the movement of the
working stroke of the piston in the accelerating tube, said means
being incorporated in the accelerating tube and arranged to
abrogate or reduce the forces acting on the piston.
2. The apparatus according to claim 1, wherein the
movement-limiting means comprises at least one opening in the
accelerating tube arranged to co-act with at least one
corresponding opening in the piston.
3. An apparatus according to claim 1, wherein said
movement-limiting means comprises at least one widened portion in
the accelerating tube.
4. The apparatus according to claim 1, wherein said
movement-limiting means comprises at least one tubular insert
arranged coaxially inside the accelerating tube.
Description
The present invention relates to apparatus for recovering the
kinetic energy bound in the wave movement of water, such as sea
waves. The apparatus includes a bouyant unit and an
energy-absorbing device connected thereto. The energy-absorbing
device comprises an immersed rigid plunger or piston slideably
arranged in a substantially vertical, elongate accelerating tube
which is intended to be immersed in said water and which is open at
both ends thereof and coupled to the bouyant unit, so as to
accompany the movement imparted to said unit by the wave
motion.
In known kinetic-energy recovering apparatus as shown in
applicant's prior patent U.S. Pat. No. 4,277,690 of this kind there
is no limit to the extent of travel of the piston within the
accelerating tube. Consequently, the piston or piston rod are
liable to be damaged when subjected to excessive forces, for
example when subjected to forces eminating from very rough or heavy
seas. In those known cases where the piston is arranged in a
widened portion of the accelerating tube, there is the further risk
of the piston striking the surfaces defining the bottom of this
widened portion, when the sea is rough or heavy, resulting in
damage to the piston or piston rod.
An object of the present invention is to provide an apparaus for
recovering the kinetic energy of water waves, having a piston which
is arranged for movement within an accelerating tube and the extent
of movement of which piston is limited in such a manner that the
force acting on the piston is greatly reduced when the piston
reaches the limit positions of said extent of piston movement.
Accordingly, there is provided an apparatus having the
characterizing features set forth in the accompanying claims.
The invention will now be described in more detail with reference
to exemplary embodiments illustrated schematically in the
accompanying drawing, in which
FIG. 1 illustrates in perspective a first embodiment of an
apparatus constructed in accordance with the invention, comprising
a bouyant unit and an accelerating tube;
FIG. 2 is a longitudinal sectional view of that part of the
apparatus shown in FIG. 1 which incorporates the limit means for
restricting the extent of piston travel and for abrogating the
force acting on the piston; and
FIG. 3 is a longitudinal sectional view of a further embodiment of
an accelerating tube in an apparatus constructed in accordance with
the invention, the Figure also showing that part of the
accelerating tube which incorporates the piston-movement limiting
means.
FIG. 4 is a longitudinal sectional view of a still further
embodiment of an accelerating tube in an apparatus constructed in
accordance with the invention, the Figure showing that part of the
accelerating tube which incorporates the piston-movement limiting
means.
The apparatus illustrated in FIG. 1 comprises mainly an
accelerating tube 1 open at its bottom end and a bouyant unit 2
mounted at its upper end. As illustrated, the apparatus is moored
by means of mooring lines 3. The bouyancy of the bouyant unit 2 and
the length of the accelerating tube 1 are such that the upper end 4
of the tube 1 lies beneath the surface of the water so that columns
of water is captured in the tube 1.
A piston 6 having an elongated rod is slidably mounted in the
accelerating tube, and in response to the changes in the column of
water captured within the accelerating tube, moves up and down
relative to the surrounding tube. The piston rod is connected but
not shown manner to means in the bouyant unit 2 for converting the
stroke of the piston relative to the bouyant unit into usable
energy. As in the known devices of this type, the column of water
within the tube 1 is substantially uneffected by the wave action of
the water, however, the tube 1 and bouyant unit 2 which float on
the water is effected by the use and fall of the water. When the
tube 1 and bouyant unit are accelerated upward by the rising water,
they move relative to the piston 6 in the substantially quiescent
column in the tube, however, an excess pressure is exerted on the
bottom of the piston 6 (i.e., on the bottom of the column of water
above the piston) while simultaneously a subpressure is exerted on
the top of the piston 6 (i.e., on the top of column of water below
the piston) due to the movement of the tube 1. Thus, the piston
would be driven upwardly and would tend to continue its upward
movement even after the tube 1 and bouyant unit 2 stop or are
reversed in their own movement. When the tube 1 and bouyant unit
are accelerated downwardly by the water, the opposite effects are
obtained. Limitations of the extent of up and down movement of the
piston is obtained by the present invention.
In the embodiment of FIG. 2, the maximum distance travelled by the
piston 6 is shown by means of the double-headed arrow 5. The piston
6 is provided with a bottom cylindrical skirt having openings 8
adjacent its upper end. The accelerating tube 1 is provided with
corresponding openings 9 in region of the lower end 10 of the
piston skirt 7. When the piston 6 is moved upwardly from the
position illustrated in FIG. 2, water is able to stream freely
through the then unobstructed openings 9, thereby to equalize the
forces acting on the piston by relieving the piston of the excess
pressure forces on its lower surface. This means that the position
in which the piston is shown in FIG. 2 constitutes the highest
position to which the piston 6 can move in the tube 1. When the
piston 6 moves downwardly the openings 8 in the cylindrical surface
of the piston skirt 7 reach a position at which they are in
register with the openings 9 in the tube 1, the water pressure
within the tube 1 and the water pressure externally of said tube
will be equalized, thereby relieving the load on the upper surface
of the piston 6. This constitutes the lowermost position to which
the piston of the embodiment illustrated in FIG. 2 can move. Thus,
the length of stroke of the piston is limited to a highest level L
according to FIG. 2, irrespective of the height of the waves.
In the FIG. 3 embodiment, the length of stroke M of a piston 11 is
restricted by an upper and a lower widening 12 and 13 respectively,
arranged in the accelerating tube 14. When the piston 11 reaches a
position, during its upward movement, at which it is accommodated
in the widening 12 the water releases its excess pressure against
the underside of the piston and rushes past the piston, into the
space between the outer cylindrical surface of the piston 11 and
the wall defining said widening 12. This causes the piston 11 to
remain in said position. Correspondingly, when moving downwardly
the piston 11 will reach a position in which it is accommodated in
the lower widening 13, and will remain in this position due to the
release of the excess pressure on the top surface of the piston
equalization of forces acting on the top and bottom working
surfaces of the piston. Thus, the working stroke of the piston is
restricted to the distance M, irrespective of the height of the
waves or the roughness of the sea.
In the FIG. 4 embodiment, the length of stroke N of a piston 15 is
restricted to the length of a cylindrical insert 16 which is
arranged coaxially inside tube 17. Insert 16 is attached to tube 17
via an upper and a lower ring 18 and 19 respectively. Between
insert 16 and tube 17 there is a filling 20. When piston 15 reaches
a position outside the insert 16 the piston 15 is guided by guides
21 and 22 until water releases its pressure against the respective
upper and lower surfaces of the piston substantially in the manner
described with reference to FIG. 3.
* * * * *